The present invention relates to an image forming apparatus capable of forming a monochrome (monochromatic) image or a color image on both sides of a paper (a plain paper, a cardboard, a postcard, an envelope, an OHP sheet or other sheet-shaped recording media). In particular, the invention relates to a technique regarding the return speed of a paper in the case that images are formed on both sides of the paper.
Recently, there has been known an image forming apparatus capable of forming a monochrome or color image on both sides of a paper in which all of the delivery speeds of the paper are increased more greatly except for the time of the transfer of an image to the paper as compared with the delivery speed of the paper in the formation of an image or the transfer of the image to the paper (for example, see JP-A-2003-50528).
In an image forming apparatus including an image forming portion for forming an image having one color on an intermediate transfer member per rotation of the intermediate transfer member or superposing images having a plurality of colors on the intermediate transfer member by a plurality of rotations of the intermediate transfer member, thereby forming a color image on the intermediate transfer member, a transfer portion for transferring the image formed on the intermediate transfer member in the image forming portion to a paper, and a fixing portion for causing the paper having the image transferred in the transfer portion to pass therethrough, thereby fixing the image onto the paper, in which the paper passing through the fixing portion can be switched back toward a return path and can be thus returned to the transfer portion so that the image can also be transferred to the other surface of the paper, a paper return speed in the formation of a color image is also increased if all of the delivery speeds of the paper except for the time of the transfer of the image are increased as in the prior art described above.
For this reason, there is a problem in that a noise made by the high-speed return is increased.